High pressure steam generator



J1me 1940- E, L. SCHELLENS El AL 5,911

HIGH PRESSURE STEAM GENERATOR 5 4 Sheets-Sheet 1 Filed Nov. 26, 1955June 25, 1940.

E; L. SCHELLENS ET AL 1 HIGH PRESSURE STEAM GENERATOR Filed. NOV. 26,1935 4 Sheets-Sheet 2 J1me 1940- IE. 1.. SCHELLENS ET AL ,9

HIGH PRESSURE STEAM GENERATOR Filed Nov. 26, 1935 I 4 Sheets-Sheet sJune 5, 1940- E. L. SCHELLENS ET AL ,91

HIGH PRESSURE STEAM GENERATOR Filed Nov. 26, 1935 4 Sheets-Sheet 4 I llPatented June 25, 1940 HIGH PRESSURE STEAM GENERATOR Eugene L.'Schellens, Bidgewood, N. J., and Christopher A. Schellens, Marblehead,Maia, assignors to 0-8 Engineering Company, Englewood, N. J., acorporation of Delaware Application November 26, 1935, Serial No. 51,618

13 Claims.

This invention relates to steam generating systems and apparatus adaptedfor the generation of steam at high pressures as around six hundredpounds per square inch and correspondingly high temperatures.

The steam generating system and apparatus of the present invention isparticularly adapted for locomotive and marine service where high powercapacity must be obtained from apparatus of restricted dimensions,although the invention has valuable features other than compactness thatrender the system and apparatus desirable for other types of service.

There are two general types of boilers, the fire tube boiler whereincombustion gases pass through tubes surrounded by water, and the watertube boiler wherein the combustion gases circulate aboutwater-containing tubes. A fire tube boiler is not practicable, however,for the direct generation of steam at pressures approximating sixhundred pounds per square inch for the purposes of this inventionbecause of the relatively great thickness of the boiler shell andassociated parts rendered necessary by the high pressures. A water tubeboiler, however, while well adapted for high pressure steam generationoccupies an objectionable amount of space for the present purposesbecause of the necessity for a large furnace and large combustion gasducts. Furthermore, the furnace requires a heat insulating lining whichwill not stand up when subjected to vibrations such as it would occurespecially in locomotive use. The present invention also comprehends acontrol of the steam generating system that extinguishes or reduces thefire when steam is not required to be made. A boiler having a heatinsulating lining in the combustion space is not susceptible to suchcontrol since the heat stored in the heat insulating lining wouldcontinue to give off heat for a considerable period of time after thefire had been extinguished or reduced, thereby nullifying the intendedeffect of the fire control.

Hence an object of the present invention is the provision of a fuelburning, steam generating system including a novel type of steamgenerator that is capable of generating large amounts of steam at highpressures and yet is compact, has only small diameter parts that aresubjected to the high pressure so that the parts can be relatively thinand yet light and has a fire box or furnace that does not necessitate aheat insulating lining.

A further objection to the use of a boiler of the ordinary type forgenerating steam at high pressure is the considerable danger of failureof a high pressure carrying tube or shell due to pitting, corrosion, orscale formation when subjected to the hot furnace gases.

The Scotch type of boiler needs no heat insulating lining for itsinternally located fire box and is capable of high output capacity forits volume but by reason of its design is suited only to low pressures.It is an object of the present invention to utilize this type of boilerfor the generation of high pressure steam by the use in the boiler of anintermediate liquid having a high vapor temperature for a low vaporpressure,

and using the vapor of the intermediate liquid for the generation ofhigh pressure steam. Thus the inherent advantages of the internal firebox type of boiler are utilized within the vapor pressures for which itis suited.

While steam can be made by piping a high temperature low pressureintermediate vapor generated in a low pressure boiler through a heatexchanger and generating high pressure steam in the tubes of theexchanger and piping the inlarge fiow of intermediate vapor required fora,

large steam power output but further may introduce complications in theway of getting the intermediate liquid vapor to the exchanger and thecondensate back into the boiler.

It" is an object of the present invention to provide means to generatevapor from the intermediate liquid and high pressure steam from thevapor in such a way as greatly to reduce the space required of thesystem and the amount of intermediate liquid, and also to greatlysimplify the exchange of heat from the intermediate liquid vapor to thesteam. I

In carrying out the above results the intermediate liquid boiler and theheat exchanger are constructed as a single unitary structure wherein thewater and steam pipes of the exchanger, in which the high pressure steamis generated, are located directly in the vapor space of theintermediate liquid boiler so that not only is the space heretoforerequired for the exchanger eliminated but the piping between the boilerand exchanger are also eliminated with the consequent elimination of anyproblems connected with conducting the intermediate liquid vapor to theexchanger and the condensate back into the boiler. Such an arrangementconstitutes an important object of the present invention.

A further object of the invention is a boiler arranged as abovedescribed, the boiler consisting of large and small drums or shells,preferably cylindrical, arranged one on top of the other and havingcommunicating open s'des admitting free vapor communication betweenthem, with the edges of the shells at the openings secured together atpoints lying in a plane perpendicular to. the plane including their axesand tied together by tie members traversing the openings; the smallshell containing the steam generating tubes and the large shellcontaining the intermediate liquid. Such a construction is inherentlystrong and compact.

A further object of the invention is the provision of a two-drum boilerconstructed as above described having parallel external ducts for thecombustion gases located on opposite sides of the small drum andcontaining water tubes and constituting economizers in which the wateris heated prior to passing to the exchanger.

It is also an object of the invention to provide the intermediate liquidboiler with fire tubes containing superheater tubes and to arrange theboiler, economizer heat exchanger and superheater so that the tubes ofthe economizer, exchanger and superheater can be withdrawn all from thesame end of the boiler.

A further object is the provision of a steam generating systemparticularly adapted to sudden variable demands, as in locomotiveservice, and wherein the generation of steam is practically immediatelyresponsive to the steam demand so that steam generation ceasesimmediately when the steam demand ceases, or the throttle is closed, andsteam is immediately made when there is a demand for steam, as when thethrottle is opened.

A yet further object is the provision of a steam generating systemwherein steam is generated by a heated intermediate fluid having arelatively large heat storage capacity which is utilized to generatesteam immediately in response to steam demand and irrespective of anytime lag between the initiation of steam demand and the heating of theinterme ate fluid.

It is another object of the invention to provide a closed cycle .steamgenerating and utilizing system having a substantially constant volumeof water therein, and a novel control system for the steam generatingsystem which includes means providing for the introduction of water intodifferent parts of the steam system automatically in response to apredetermined steam pressure and also in response to a predeterminedwater level in a water storage or hot well.

A yet further object is the provision of a control system for the steamgenerating system wherein water is introduced into the high pressuresteam between the heat exchanger and the superheater under control ofthe steam pressure for the purpose of maintaining a constant steampressure under certain conditions of operation of the system.

A further object is generally to improve upon high pressure steamgenerating systems and apparatus.

Fig. 1 is a sectional elevation taken through the longitudinal axis ofthe steam generator forming a part of the present invention.

Fig. 2 is a front end view of the steam generator of Fig. 1, one-half ofthe view being a section taken along line 2-4 of Fig. 1.

Fig. 3 is a sectional detail taken along line 3-4 of Fig. 1 andillustrating in cross-section the super-heater header and theeconomizers.

Fig. 4 is an end detail of the upper back end or the boiler.

Fig. 5 is a view of the inner face of the heat exchanger cover plate,looking in the directionof present invention is illustrated in Fig. 1.It comprises a cylindrical outer shell I! having front and back heads i4and I6, respectively. The boiler is of the Scotch marine type and has aninternal flre box or combustion chamber extended substantially theentire length of the boiler and comprised of the cylindrical corrugatedshell ii, the front head 20 to which the front end of the shell I8 issecured, the intermediate head 22 to which the rear end of the shell isconnected, and the back head 24 which is connected to the intermediatehead 22 by a cylindrical plate 26. The front head 20 of the fire box andthe front head I4 of the boiler are conveniently provided with alignedapertures 28 surrounded by connected flanges 29, through which aperturesfuel is introduced into the fire box. In practice the heads 20 and I4and 24 and IE will be stayed together in the usual manner not necessaryto illustrate herein. A plurality of fire tubes 30 extend from theintermediate flre box head 22 above and parallel with the fire box shelland through the front boiler head l4 and are disposed arcuately aboutthe upper part of the fire box.

In accordance with this invention water-carrying steam-generating tubesare disposed within the boiler above the intermediate liquid level andin direct contact with the vapor therein. Since, however, provision forthe tubes inside the shell I! of the boiler would result in anundesirable enlargement of the diameter of the shell and also require astronger shell, the tubes are disposed in a secondary boiler shell 32which is disposed on top of and parallel with the shell l2 and issubstantially the length of said shell and is open for freecommunication therewith through substantially its entire length. To thisend the top portion of the shell I2 is provided at its top with anopening 34 that extends substantially the length of the shell, or theends 36, see also Fig. 2, of the shell sheets are spaced apart toprovide the opening. The ends 36 are also shaped to lie in a horizontalplane. The shell 32 or the heat exchanger is similarly constructed or isprovided with a longitudinally directed opening 38 between the spacedends 40 of the shell sheets thereof, the opening extending substantiallythe length of the shell. The ends 40 are similarly flattened into ahorizontal plane. A tie plate 42 is disposed between the flattened endsand 40 of the two shells and the ends of the sheets of the two shellsare secured to said tie plate in a fluid tight manner by welding orotherwise. The plate 42 is provided with a longitudinal series of largeopenings 44 with interposed tie sections 46 which connect andtietogether the ends of the shell sheets on opposite sides of theopenings. This arrangement of uniting the shells together is simple andThe steam generator comprising a part of the head 48 and the front endis removably closed by a head 50 in which are expanded or otherwisesecured the ends of a plurality of groups of heat exchanger tubes 52,the open ends of the tubes being surrounded by a continuous housingflange 54, the open end of which is closed removably by a cover 56having an inlet passage 58 for water and an outlet passage 60 for steam.The housing 54 and its cover 56 are provided with registering partitionwalls. Said walls consist of a vertical partition 62, an upperhorizontal partition I54 and a lower horizontal partition 69. thepartitions being joined together and to the housing to form between themchambers permittin fluid flow in series between the various groups ofheat exchanger tubes. The arrangement is such that water flows throughthe inlet 59 into the chamber 010. and into the left hand open ends ofthe top-most group 52a of tubes. see Fi 2. and through these tubes tothe back of the boiler. and thence through the return bends andforwardly to the interior of the chamber and into the chamber 61b andfrom said chamber into the open right hand ends of the next lower group52b of tubes and through these tubes and into the chamber 61c and thenceinto the left hand end of the lowermost group of tubes 52c and throughthese tubes and into the chamber 61d and into the outlet passage 60. Thecross-sectional area of the steam passage through the heat exchanger isprogressively increased from the inlet to the outlet by increasing thenumber of tubes in the groups to accommodate the increase of volume ofthe fluid approximately in proportion as it becomes converted from waterto steam.

The groups of heat exchanger tubes 52 with the front head 50 can beremoved as a unit from the shell 32 when desired. the tubes beingsupported in a suitable conventional manner on tracks 68.

The level of the intermediate liquid in the boiler is at some locationabove the top of the fire tubes 30 and the smoke box shell 26 butpreferably below the plate 42 or at least below the heat exchanger tubes52. The heat exchanger tubes are thus immersed directly in theintermediate fluid vapor of the boiler and the vapor has free access tothe tubes. Any suitable intermediate liquid may be employed that has asufficiently low vapor pressure at the temperature desired to generatethe required steam pressure.

The present boiler is designed to generate steam at six hundred poundspressure and the intermediate liquid selected for the purpose is onehaving a vapor pressure of around thirty pounds per square inch and atthis pressure having a vapor temperature of around 600 F. Thistemperature is satisfactory for generating steam at six hundred poundsper square inch. The low vapor pressure of the intermediate liquidpermits the use of the Scotch type of boiler herein illustrated with avery light and yet perfectly safe construction. The particularintermediate liquid selected for the purpose is diphenyloxide which isstable at the temperatures employed and is relatively inexpensive incomparison with other mediums having approximately the same vaportemperature and pressure.

the chamber 10, receiving superheated steam from the superheater tubesand the other chamber 80 receiving steam from the heat exchanger.Similar outer ends I2 of the superheater coils are connected with thechamber I9 and the similar inner ends 14 of the superheater coils areconnected with the chamber 80. Since the fire tubes 30 are arranged inarcuate lines having a common center which is also the center for thearcuate superheater header, but one type of superheater unit is neededfor installation in any one of all the fire tubes.

Steam from the heat exchanger is not passed directly into'thesuperheater header but is passed first into the interior of a separatordrum 82, the steam outlet 60 of the heat exchanger being connected witha pipe 84 which extends into the drum 82. Another pipe 86 conducts steamfrom the separator to the steam inlet 89 of the saturated steam chamber18 of the header, the inlet 18 being located at one end of the header.The outlet 90 for the superheated steam from the chamber 80 is locatedat the other end of the header. The separator 92 is adapted at. times toreceive water to be evaporated by the steam therein for the purpose ofcontrolling the steam pressure, as will be explained in greater detailhereinafter.

The combustion gases from the fire tubes 90 are discharged into anarcuate combustion gas header 92 of which the superheater header I6constitutes the bottom wall and the front boiler head I4 the rear wall.An arcuate top wall 94 is provided which is suitably secured to thefront boiler head and a removable front wall 96 constitutes a closurefor the chamber 92, the front wall being removable for the purpose'ofgaining,

access to the superheater and fire tubes.

A pair of economizer casings 98 and I00, generally rectangular incross-section, are disposed above the boiler shell I2 and extendlengthwise thereof on opposite sides of the vapor containing shell 92.The front ends of said casings are in communication with the gas header92 through ing through the top wall 94 of the header. The casings at theback of the boiler communicate with a cross header I04 provided with astack connection I06.

The economizer casing 99 is occupied by a vertical series of loopedwater tubes I09 making a plurality of horizontal passes lengthwise ofthe casings. The economizer casing I00 is provided with a similar seriesof water tubes H0. The

ducts I02, of which one is shown in Fig. 2, opensimilar ends of all ofthe tubes of the casing I00 into the lower series of tubes below thediaphragm and thence into the header H4 and upwardly in this header intothe upper series of tubes and thence from these tubes back into theheader I I2 above the diaphragm. With this arrangement the series oftubes in the economizer casing I00 are separated into two sets that areconnected in series. The water thence passes from the outlet of theheader II2 through a cross-over pipe I20. into a header I22 similar tothe header H2 and associated with the tubes of the economizer casing 98.The water in said header I22 passes in series through the two sets oftubes in said casing, by reason of the diaphragm I24 in said header, andthence out of the outlet I28 of the I header H2 into a pipe I28 andthence into the inlet 58 of the heat exchanger.

The connection between the economizer, heat exchanger and superheater issuch that the water passes first through the economizer tubes where itreceives heat from the partly cooled combustion gases surrounding thetubes and thence passes into the heat exchanger tubes where the water isconverted into steam by reason of the high temperature vapor of theintermediate liquid of the boiler. The steam passes from the heatexchanger tubes into the. separator 82 and thence through thesuperheater tubes. The superheated steam passes from the outlet of thetube through a suitable pipe I20 to the prime mover.

The steam generating system and certain of its controls is illustrateddiagrammatically in Fig. 7. The boiler is here shown as flred with oilby an oil burner I22 receiving oil from a pipe I34. The operation of theburner is adapted to be controlled by pressure conditions of the vaporof the intermediate fluid. The intermediate fluid boiler I2 is providedwith a pressure controlled oil throttle valve I36 which is interposed inthe line 'of the oil pipe I34 and is so arranged, as by the diaphragmI36a and the piston valve Ilib (having the oil throttling passage I000therethrough) that comes up against the end of its cylinder when theintermediate fluid pressure is sufficiently high, that as pressure ofthe vapor of the intermediate fluid increases above a certain point thesupply of oil is gradually diminished and when the vapor pressurereaches a predetermined maximum point-the oil supply is diminished to anidling capacity suiflcient merely to maintain vapor pressure when nomaterial amount of steam is being made. This method of control serves tomaintain a substantially constant intermediate vapor pressure under allconditions of operation and also to prevent the generation of unsafepressures.

While the burner is herein shown as oil fired the boiler also isparticularly adapted for burning powdered fuel by reason of its largecombustion chamber.

The system herein shown operates in a closed cycle. all of the steamgenerated being condensed and the condensate being recirculated to bereconverted into steam. Thus the amount of water in the system issubstantially constant and additional water is only required to beintroduced infrequently into the system.

The high pressure superheated steam passes from the pipe I into theprime mover I38, which may be a turbine or the like. The exhaust steamfrom the prime mover passes into a condenser I40 where the steam iscondensed. Air from the condenser is extracted by an air pump Thecondensed water is withdrawn from the condenser by a condenser waterpump I44 and discharged through a non-return check valve I40 into a hotwell I40. Water is withdrawn from the hot well by a continuouslyoperating boiler feed water pump I and forced through a pipe I52, acontrol valve I04 and a pipe I50 into the inlet of the economizer 90,I00. The water thence flows in the manner described above through theheat exchanger 32 where it is converted into steam and thence into theseparator 02 and from the separator through the superheater 10.Preferably all the pumps and moving accessory apparatus of the systemare electrically operated.

Make-up water when required is introduced into the hot well through apipe I00. The makeup water preferably is distilled and hence is freefrom air and scale forming materials. The valve I54 is controlledthrough a float I by the level of water in the hot well. The arrangementis such that the flow of water from the boiler feed pump I60 into thewater heating and steam generating sections of the boiler is restrictedwith low water level in the hot well and permitted with high water levelin the well. The movable valve member I82 of the valve, see Fig. 8, isprovided with a small passage I 04 therethrough or some equivalentarrangement is made whereby a small amount of water is permitted to passthrough the system when the valve is closed.

A branch pipe I66 leads from the high pressure outlet of the boiler feedwater pump I50 and conducts water through a non-return valve Ill andthrough a pressure controlled valve I10 to the interior of the separator82. The pressure controlled valve I10, of which a suitable type is 11-lustrated in Fig. 10, is operated by a bellows I 12 or equivalent meanssupplied with pressure steam through a pipe I14 from the interior of theseparator B2. The arrangement is such that when the pressure in theseparator is above a certain predetermined value-the valve I10 is causedto open to admit water into the separator. The steam in the separatorevaporates the water and hence the result is a reduction oi pressure ofthe steam. With a sumcient reduction of pressure the valve I10 closes.Thus the steam pressure is maintained substantially constant.

'A small transfer pump I16 may be provided which is adapted to beoperated at the time the system. is conditioned for operation for thepurpose of withdrawing what water there may be in the separator 02 andreturning it to the hot well.

A vent line I18 connects the space above the water level in the hot wellwith the condenser I40.

The operation of the system herein illustrated is essentially asfollows:

The hot well is first brought to its full condition of water by theoperation of the transfer pump I16 which pump can be stopped after theseparator is empty. The oil burner I32 is then started in operation atidling capacity from energy drawn from any suitable outside source asstorage batteries. The combustion gases are preferably circulatedthrough the steam generating apparatus by a motor driven exhaust fan I19which is connected to the combustion gas outlet I06 of Fig. 1. Thisexhauster is also started in operation at idling speed. In due course oftime the oil burner heats up the intermediate fluid in the boiler andcauses it to vaporize and to build up a normal operating pressuretherein.

which pressure will be maintained substantially constant by theoperation of the pressure controlled oil valve I36. The boiler feedwater pump I50 can then be started in operation. Since the hot well isfull of water and the float controlled valve I54 is open the waterpasses into the heating coils of the generator and steam is generatedfrom the heat of the combustion gases and from the heat of theintermediate liquid vapor. Steam can then be directed into the primemover to develop load.

The initial circulation of water through the system tends to reduce thevapor pressure within the boiler and thereby increase the amount of fuelfed to the oil burner and burned in the furnace. When the maximumworking steam pressure is attained the pressure operated control valveI10 starts to open and admits the relatively cold water from the hot'well under pressure of the feed.

exchanger will result in the throttling of the oil supply to the oilburner.

The presence of water in the separator results in a lowering of thesteam pressure due to the evaporation of the water by the heat of thesteam so that the steam pressure, is thereby maintained substantiallyconstant. As the separator steam pressure drops the pressure controlledvalve I'lIl begins to close and closes at a predetermined low pressure.The water from the boiler feed water pump I50 can then re-circulatethrough the economizer and heat exchanger and again generate steamtherein. Intermediate conditions of operation will resultin a graduatedcontrol tending to hold the separator steam pres-' sure substantiallyconstant. That is to say, when the valve I10 is partly closed a certainamount of water from the boiler feed water pump passes into theeconomizer and heat exchanger and is converted into steam' therein and acertain amount of water passes into the separator and is converted intosteam therein. Thus steam is'generated in both parts and the operationis such as to hold the steam pressure substantially constant.

The water accumulation in the separator 82 due to the operation of thepressure controlled valve I10, as above described, and also due to anymoisture in the steam passing into the separator and settling outtherein is automatically compensated for by the float controlled valveI54. Since the amount of water in the steam circulating system isconstant any water that is not in the hot well must be in the separatorand vice versa. Thus when the hot well is full the separator must beempty, and when the separator has considerable water in it there is acorresponding absence of water from the hot well. With the float,controlled valve I54 so arranged that it closes when the level of waterin the hot well is low and opens when the level is high steam generationand pressure control is automatically accomplished. For instance,when-the level of water in the hot well is at a maximum height there canbe no substantial amount of water in the separator and hence steam mustbe generated by water circulated through the economizer and heatexchanger tubes. When, however, the water levelis at its lowest point inthe hot well the separator 82 must have its maximum amount of water andhence steam can be generated by the evaporation of the water in theseparator. At some intermediate level'of water in the hot well the floatcontrolled valve will be partly closed and steam will be generated bothby the circulation of water through the economizer and heat exchangerand by the evaporation of the water in the separator.

When the water level is at its lowest in the hot well and the separatorhas then its maximum amount of water, and since the water therein isrequired to be converted into steam by the flow of superheated steaminto the separator, it is necessary to provide a small by-pass aroundthe float controlled valve I54, which by-pass is conveniently providedby the passage I84 through the movable valve member of the valve. Thesize of the by-pass is adjusted to admit sufficient water through theeconomizer and the heat exchanger to vaporize the water in theseparator. Since the amount of water circulating through the -heatexchanger at this time is relatively small the steam generated in theheat exchanger will be superheated and this superheat is effective inevaporating the water in the separator and maintaining substantiallyconstant pressure under the demands of the prime mover until the waterlevelin the hot well is again restored and normal feed continued. Steamis also generated in the separator by the evaporation of some of thewater therein in response to a reduction of steam pressure.

It is, ofcourse, apparent that the water capacity of the hot well,together with that of the abnormal reduction of water level. With thepresent system even if the boiler feed water system is allowed to rundry no damage can result. In this case the intermediate fluid pressurewill cause the burner to be shut down so that the temperature of thegases in the economizer is not high enough to cause damage to the tubeseven if they are empty of water. For the same reasons the superheatertubes can suffer no damage. The heat exchanger tubes can obviouslysuffer no damage since the temperature of the vapor of the intermediatefluid is held down by reason of the pressure control of the burner. Theboiler, per so, cannot run dry since there is no abstraction of theintermediate liquid or its vapor.

The accessories of the system, such as the oil burner, the float valveI54, and the pressure valve I10, the oil valve I36, are generallystandard pieces of apparatus of proved reliability, operating in theirintended manner in the present system and contributing their ownreliability to that of the system.

While the pressure of the intermediate fluid vapor is maintained at notgreater than a predetermined safe maximum pressure by the automaticoperation of the oil burner, a safety valve I'Hi, see Fig. 1, isprovided as a precautionary measure.

The heat exchanger tubes 52 are preferably of small cross-section sothat if one should burst for some unforeseen reason the volume of steamthat can be forced through the ruptured zone into the vapor space of theboiler can amply be taken care of by the safety valve. The exchangertubes preferably are made of Monel metal which is not subject topitting. Pitting is largely due to the presence of air in the water incontact with which air cannot enter or is removed by the condenser airpump the danger of pitting of any of the tubes is quite remote. Scaledeposits, even if present on the inner surfaces of the heat exchangertubes do not lower the high standard of safety provided by the presentsystem since the tubes are subject only to the temperature of theintermediate vapor and not to the radiant heat of the fire or the highlyheated combustion gases thereof which high temperature is the cause oftube failures due to scale deposits.

There is also a substantial absence of pitting of the boiler surfaces incontact with the intermediate fiuid and subjected to the radiant heat ofthe fire and the temperature of the combustion gases by reason of thenature of the intermediate fiuid, the characteristics of which prohibitthe pitting of the heat transfer surfaces and the fouling thereof by ascale formation which is one of the main operating difilculties ofboilers and particularly locomotive boilers.

While the steam pressure is high the actual pressure acting on theboiler structure is very low, being of the order commonly associatedwith house heating boilers. Hence the structure can be extremely light,not only because of the lower pressure but also because, due to theinertness of the intermediate liquid, no allowance need be made forcorrosion.

Due to the location of the combustion chamber entirely within the boilerand practically completely surrounded by the intermediate liquid no heatinsulating lining for the combustion chamber is required, which makesthe system especially adapted for locomotive use and for use in otherlocalities where the boiler is subject to excessive vibration. Since thefire box is entirely surrounded by the intermediate liquid the radiantheat of the fire is utilized very effectively in heating the liquid sothat the boiler has inherently a high power capacity for its volume. Theabsence of heat insulating linings is also advantageous, in that thereis thereby assured a rapid response of the system to load changes,without the generation of uncontrollable excessive intermediate vaporpressures and also without the loss of vapor through safety valves thatwould otherwise occur upon sudden cessation of steam demand, because ofthe stored heat in the lining which would be given up to the liquid foran appreciable length of time following the drop of steam fiow andreduction of the fire.

The system can supply steam instantly upon demand, without time lag, dueto the heat storage capacity of the intermediate liquid, since the vaporpressure of the liquid is automatically maintained substantiallyconstant.

Cessation of steam demand from full capacity operation also results inprompt cessation of steam generation since, due to the generation ofsteam in the separator, the heat exchanger and economizer are not fullof water, as would otherwise be the case, that would be converted intosteam after the demand had ceased, which steam would build up excessivepressure that would have to be released through a safety valve.

The Scotch type of boiler also is particularly suited for use with anintermediate liquid, because its large fire box provides for arelatively low rate of heat transfer to the intermediate liquid and thusavoids any tendency toward breakdown of the chemical structure thereof.The large fire box also is advantageous, in combination with thesuperposed vapor shell, in that the liquid volume is small so that theexpense of filling the boiler with its initial charge of relativelyexpensive intermediate liquid is kept down.

It is apparent that the construction of the system and of the apparatusthereof and the method of operating the system can be modified largelywithout departing from the spirit of the invention.

We claim:

1. A unitary intermediate liquid high pressure steam generatorcomprising a boiler shell having an internal combustion chambersubmerged in the intermediate liquid, fire tubes extending from thecombustion chamber through the boiler below the intermediate liquidlevel, water tubes in the vapor space of the boiler above the liquidlevel, and steam superheater tubes in the fire 311?: connected toreceive same from the water 2. A steam generator comprising anintermediate liquid. boiler having an internal combustion chamberlocated in the bottom part of the boiler, fire tubes extending from thecombustion chamber through the end of the boiler and disposed above thecombustion chamber parallel with the axis of the boiler and distributedin an arcuate line about said combustion chamber, superheater tubes insaid fire tubes, a superheater header carried by the end of the boiler,said header being arcuate in correspondence with the arcuatedistribution of the fire tubes and being within the arcuate line of saidtubes and having superheated and saturated steam chambers connected withsaid superheater tubes, and water tubes in the vapor space of saidboiler having a connection with said saturated steam chamber.

3. A steam generator unit comprising an intermediate liquid boilerhaving an internal combustion chamber, steam-generating water tubes inthe vapor space of said boiler, fire tubes extending from saidcombustion chamber through an end wall of the boiler, superheater tubesin said fire tubes, a superheater header connected with said superheatertubes and having a connection with said steam-generating water tubes, acombustion gas header in front of said fire tubes, economizer casingslocated on top of said boiler and extended lengthwise thereof and havingcommunication with said combustion gas header, water tubes in saideconomizer casings, and means connecting said water tubes with saidsteam-generating water tubes.

4. A steam generator comprising an intermediate liquid boiler comprisinga'large lower shell and 'a small upper shell, said shells having meansproviding free fiuid circulation therebetween throughout the major partof their common length, said lower shell adapted to contain a highboiling point low vapor pressure liquid, and said upper shell adapted tocontain the vapor only of said liquid, steam generating tubes locatedwithin the upper shell and in contact with the vapor only, and acombustion chamber located internally of said lower shell beneath theliquid level therein.

5. A steam generator comprising an intermediate liquid boiler includinga large liquid containing shell containing an internal combustionchamber and adapted to contain a high boiling temperature low vaporpressure liquid, a smaller upper vapor containing shell parallel withsaid first shell, both shells having registering longitudinallyextending openings therein, an apertured tie plate interposed betweensaid shells and secured to both around the openings thereof,

said upper shell providing a vapor chamber'for the vapor generated insaid lower shell, and steam generating tubes located in said upper shellin contactwith the vapor therein.

6. A steam generator comprising an intermediate liquid boiler includinga large liquid containing shell containing an internal combustionchamber and adapted to contain a high boiling temperature low vaporpressure liquid, a smaller upper vapor containing shell parallel withsaid first shell, both shells having registering longitudinally extendedopenings therein, an apertured tie plate interposed between said shellsand secured to both around the openings thereof, said upper shellproviding a vapor chamber for the vapor generated in said lower shell,steam generating tubes located in said upper shell in contact with thevapor therein, fire tubes extending from said combustion chamber throughan end wall of said lower shell, superheater tubes in said fire tubes,and a superheater header connected with said superheater tubes.

7. A steam generating unit comprising an intermediate liquid boilerincluding a large liquid.

containing shell containing an internal combustion chamber and adaptedto contain a high boiling temperature low vapor pressure liquid, asmaller upper vapor containing shell parallel with said first shell,both shells having registering longitudinally extended openings therein,an apertured tie plate interposed between said shells and secured toboth around the openings thereof, said upper shell providing a vaporchamber for the vapor generated in said lower shell, steam generatingtubes located in said upper shell in contact with the vapor therein,fire tubes extending from said combustion chamber through an end wall ofsaid lower shell, superheater tubes in said fire tubes, a superheaterheader carried by said end wall of said shell and connected with saidsuperheater tubes, a combustion gas header located above saidsuperheater header and in communication with said fire tubes, economizercasings extended lengthwise of said shells above said lower shell and onopposite sides of said upper shell and having means establishingcommunication between them and said combustion gas header, economizertubes in said casing, and means connecting said economizer, heatexchanger and superheater tubes in series relation.

8. A steam generating system comprising an intermediate liquid boiler,heating means for the liquid in said boiler, steam generating means incontact with the vapor of said intermediate liquid, means responsive tothe pressure of the vapor of said intermediate liquid operable tocontrol the rate of heating of said liquid to maintain a substantiallyconstant vapor pressure irrespective of the rate of steam generation, asteam and water circulating system connected with said steam generatingmeans, and means responsive to the steam pressure operable to regulatethe admission of water to a part of said system containing steam tomaintain a substantially constant steam pressure.

9. A steam generating system comprising an intermediate liquid boiler,heating means for the liquid in said boiler, steam generating means incontact with the vapor of said intermediate liquid, means responsive tothe pressure of the vapor of said intermediate liquid operable tocontrol the rate of heating of said liquid to maintain a substantiallyconstant vapor pressure irrespective of the rate of steam generation, asteam and water circulating system connected with said steam generatingmeans, and means to maintain a substantially constant steam pressurecomprising means responsive to steam pressure to admit water into asteam space of said circulating system.

'10. A steam generating system comprising an intermediate liquid boiler,water-containing steam-generating tubes in theyapor space of saidboiler, a closed steam circulating system connected with said tubes, ahot well in said system for the condensate, means for introducing waterinto said tubes from said hot well, and means responsive to steampressure in said system to admit water from said hot well into the steamof said steam circulating system when the steam pressure is high, andmeans responsive to water level in said hot well to admit water intosaid steam generating tubes when the hot well water level is high.

11. A closed circuit steam generating system comprising steam generatingmeans, steam condensing means, a steam conduit connecting said means, ahot well in the system between the condensing and the steam generatingmeans, a reservoir for water in said conduit and through which reservoirpower generating steam flows between the steam generating means and thecondensing means, means for passing water from said hot well into saidsteam generating means, means responsive to a high level of water insaid hot well for admitting water into said steam generating means, andmeans responsive to a predetermined pressure of steam in said reservoirfor admitting water therein from said circulating means to reduce thepressure and to be vaporized and mix with the pressure steam and toproduce additional steam.

12. A steam generating system comprising an intermediate liquid boiler,fuel burning means for heating the liquid in said boiler, steamgenerating tubes in the vapor space of said boiler, superheater tubes inthe combustion gases of said heating means, piping connecting said steamgenerating tubes and said superheater tubes and including an interposedseparator, means for condensing the steam, a hot well receiving thecondensate, a boiler feed water means receiving water from said hot welland normally arranged to direct the water into said steam generatingtubes, means responsive to the level of water in said hot well forcontrolling the flow of feed water into said tubes and operable torestrict the flow of feed water when the water level in the hot well islow, and means responsive to steam pressure in said separator foradmitting water from said feed water means thereto and operative toadmit water when the steam pressure is above a predetermined value.

13. A boiler having superimposed, parallel, intersecting approximatelyco-extensive large and small shells opening into each otherapproximately throughout their lengths, said large shell beingapproximately filled with a high-boilingtemperature, low-pressureliquid, a combustion chamber surrounded by said liquid, a combustion gasflue leading from said combustion chamber through said liquid, a steamgenerating tube located in the vapor space of said small boiler shelland heated by the vapor thereof, and a superheater tube connected withsaid steam generating tube and located in said flue.

EUGENE L. SCHELLENS. CHRISTOPHER A. SCHELLENS.

